Table of Contents

Name

owcapi - easy C-language 1-wire interface

Synopsis

libowcapi library to link with your program

Initialization

ssize_t OW_init( device name or full parameter string )
ssize_t OW_init_args( int argc, char ** args )

The full set of initialization options is extensive. They correspond roughly to the command line options of owfs (1) owhttpd (1) and owftpd (1)

Get data

int OW_get{ const char * path, char ** buffer, size_t * buffer_length )
ssize_t OW_lread( const char * path, unsigned char * buffer, const size_t size, const off_t offset )

Set data

ssize_t OW_put{ const char * path, const char * buffer, size_t * buffer_length )
ssize_t OW_lwrite( const char * path, const unsigned char * buffer, const size_t size, const off_t offset )

Close

void OW_finish{ void )

Functions

OW_init

OW_init_string offers the full flexibility of the owfs (1) and owhttpd (1) command line.
Arguments
Can be as simple as jus the device name, a full parameter specification. One or more device names (includes tcp, serial, usb...) and command line switches. See owfs (1) for full syntax.
Returns
0 for success. -1 on error and errno will be set. OW_finish does not need to be called if OW_init fails.
Sequence
One of the init functions must be called before accessing the 1-wire bus. OW_finish is optional.

OW_init_args

OW_init_args offers the full flexibility of the owfs (1) and owhttpd (1) command line.
Arguments
One or more device names (includes tcp, serial, usb...) and command line switches. See owfs (1) for full syntax. Unlike OW_init_string the arguments are in argv/argc format.
Returns
0 for success. -1 on error and errno will be set. OW_finish does not need to be called if OW_init fails.
Sequence
One of the init functions must be called before accessing the 1-wire bus. OW_finish is optional.

OW_get

OW_get is used to get directory listings and file contents. The results are put in a dynamically allocated buffer.
Arguments
path is the path to the directory or file (property). *buffer returns a pointer to a buffer containing the directory (comma separated) or value. buffer_length returns the length of the value/string in buffer
Returns
number of bytes on success. -1 on error (and errno is set).
Sequence
One of the init functions must be called before accessing the 1-wire bus. OW_finish is optional.
Important note
buffer is allocated ( with malloc ) by OW_get but must be freed in your program. See malloc (3) and free (3)

OW_lread

OW_lread is used to read 1-wire memory chips. Think of it as a combination of lseek and read It allows random-access to the memory, specifying location and length. Unlike OW_get directories cannot be obtained and the buffer must be pre-allocated rather than allocated by the routine. buffer must be at least size length.
Arguments
path is the path to the file (property). buffer is the (pre-allocated) memory area where the value will be placed. size is the length of bytes requested. offset is the position in file to start reading.
Returns
number of bytes on success. -1 on error (and errno is set).
Sequence
One of the init functions must be called before accessing the 1-wire bus. OW_finish is optional.

OW_put

OW_put is an easy way to write to 1-wire chips.
Arguments
path is the path to the file (property). buffer is the value to be written. buffer_length is the length of the value buffer. Returns number of bytes on success. -1 on error (and errno is set).
Sequence
One of the init functions must be called before accessing the 1-wire bus. OW_finish is optional.

OW_lwrite

OW_lwrite is the companion of OW_lread. It allows writing to arbitrary positions in 1-wire memory. Think of it as a combination of lseek and write. buffer must be at least size length.
Arguments
path is the path to the file (property). buffer is the data to be written. size is the length of bytes to be written. offset is the position in file to start writing.
Returns
number of bytes on success. -1 on error (and errno is set).
Sequence
One of the init functions must be called before accessing the 1-wire bus. OW_finish is optional.

OW_finish

OW_finish cleans up the OWFS 1-wire routines, releases devices and memory.
Arguments
None.
Returns
None
Sequence
OW_finish is optional since cleanup is automatic on program exit.

Description

1-Wire

1-wire is a wiring protocol and series of devices designed and manufactured by Dallas SemicondUctor, Inc. The bus is a low-power low-speed low-connector scheme where the data line can also provide power.

Each device is uniquely unalterably numbered during manufacture. There is a wide variety of devices, including memory, sensors (humidity, temperature, voltage, contact, current), switches, timers and data loggers. More complex devices (like thermocouple sensors) can be built with these basic devices. There are also 1-wire devices that have encryption included.

The 1-wire bus is accessed via one of a number of serial, parallel, i2c, network or USB adapters.

OWFS design

OWFS is a suite of programs that fundementally make the 1-wire bus and its devices easily accessible. The underlying priciple is to create a virtual filesystem, with the unique ID being the directory, and the individual properties of the device files.

There is optional data caching to improved performance, but possible confusion over stale data.

libowcapi

libowcapi (1) is an encapsulation of the full libow library for C programs.

libowcapi (1) allows a C program to use OWFS principles (consistent naming scheme, multiple adapters, devices, and compatibility) directly from a C program. There are analogous modules for other programming languages:

C
libowcapi
perl
owperl
php
owphp
python
owpython
tcl
owtcl

Example

/* Simple directory listing -- no error checking */
#include <owcapi.h>
unsigned char * buf;
size_t s ;
OW_init("/dev/ttyS0");
OW_get("/",&buf,&s) ;
printf("Directory %s0,buf);
free(buf);
OW_finish() ;

See Also

Programs

owfs (1) owhttpd (1) owftpd (1) owserver (1) owdir (1) owread (1) owwrite (1) owpresent (1) owtap (1)

Configuration and testing

owfs (5) owtap (1) owmon (1)

Language bindings

owtcl (3) owperl (3) owcapi (3)

Clocks

DS1427 (3) DS1904(3) DS1994 (3) DS2404 (3) DS2404S (3) DS2415 (3) DS2417 (3)

ID

DS2401 (3) DS2411 (3) DS1990A (3)

Memory

DS1982 (3) DS1985 (3) DS1986 (3) DS1991 (3) DS1992 (3) DS1993 (3) DS1995 (3) DS1996 (3) DS2430A (3) DS2431 (3) DS2433 (3) DS2502 (3) DS2506 (3) DS28E04 (3) DS28EC20 (3)

Switches

DS2405 (3) DS2406 (3) DS2408 (3) DS2409 (3) DS2413 (3) DS28EA00 (3)

Temperature

DS1822 (3) DS1825 (3) DS1820 (3) DS18B20 (3) DS18S20 (3) DS1920 (3) DS1921 (3) DS1821 (3) DS28EA00 (3) DS28E04 (3)

Humidity

DS1922 (3)

Voltage

DS2450 (3)

Resistance

DS2890 (3)

Multifunction (current, voltage, temperature)

DS2436 (3) DS2437 (3) DS2438 (3) DS2751 (3) DS2755 (3) DS2756 (3) DS2760 (3) DS2770 (3) DS2780 (3) DS2781 (3) DS2788 (3) DS2784 (3)

Counter

DS2423 (3)

LCD Screen

LCD (3) DS2408 (3)

Crypto

DS1977 (3)

Pressure

DS2406 (3) -- TAI8570

Availability

http://www.owfs.org

Author

Paul Alfille (palfille@earthlink.net)


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